1. Field of the Invention
The present invention relates to a housing of a portable information terminal such as a notebook PC, a PDA or a game machine and more particularly to a reinforcing of the structure of the portable information terminal. The present invention also relates to a method of reinforcing the housing and to a portable information terminal using the housing.
2. Background of the Related Art
In recent years, with the increasing need to reduce the weight and thickness of portable information terminals, such as notebook PCs, PDAs, and game machines, the strength of housings of portable information terminals has become critical. In other words, based upon market demands, it has become necessary to minimize the thickness of a housing of a portable information terminal in order to reduce the weight and thickness of the portable information terminal. However, a reduction in the thickness of a housing of a portable information terminal, may often result in failure to provide the structural strength required for the portable information terminal.
For instance, FIG. 6 shows the construction of an ordinary notebook PC as an example of a portable information terminal. In the example shown in FIG. 6, the notebook PC 51 is constructed by attaching a keyboard unit 53 and an LCD panel 54 to a housing 52 made of, for example, electrically conductive CFRP. Attempts have been made to reduce the thickness of the housing 52 in the thus-constructed notebook PC 51 to such a limit as to satisfy the recent weight/thickness reduction requirements. In actual use, however, particularly when a user holds between his or her fingers one or both of two front corners A and B closer to the user as shown in FIG. 6 while the LCD panel 54 is set in the operating state, an excessively large force is applied to the housing 52 through leverage by the weight of the main body of the notebook PC 51 and the weight of the LCD panel 54 with the center of gravity shifted rearward. A design for reducing the weight and thickness of the notebook PC 51 is restricted because of this problem.
Also in the notebook PC 51, a metallic base plate constituting the keyboard unit 53 is maintained at ground level to enable the keyboard unit 53 to function as a shielding plate for shielding against external noise and electric wave noise emitted from the PC itself. However, as the notebook PC is further reduced in weight and thickness, the space in the housing 52 becomes so small that it is difficult to maintain the keyboard unit 53 at ground level. Thus, there is a problem that the keyboard unit 53 is not sure to perform the function of a shielding plate for shielding against external noise and electric wave noise emitted from the PC itself.